1. Field of the Invention
The present invention relates to an electrochromic (hereinafter, referred to as EC) device in which the color during the coloring mode has been realized that the color is gray.
2. Description of the Related Art
The EC device is a device for reversibly executing the coloring and the bleaching using EC phenomenon, and is used for a dimming rearview mirror, a dimming glass, a display device and the like. An example of a section of the laminated structure of the conventional EC device is shown in FIG. 2. In this example, the entire device is constructed to be transparent. An ITO (Indium Tin Oxide) transparent electrode film 12, constituting a lower electrode film, is formed on a transparent glass substrate 10; and a mixture film 14 of iridium oxide and tin oxide constituting an oxidation coloring layer, a tantalum oxide film 16 constituting a solid-state electrolyte layer, a tungsten oxide film 18 constituting a reduction coloring layer and an ITO transparent electrode film 20 constituting an upper electrode film are sequentially formed on the ITO transparent electrode film 12. An end portion of the lower ITO transparent electrode film 12 is previously provided with a partition 22 using a laser etching and an area 12a of the end portion is electrically isolated. An end portion of the upper ITO transparent electrode film 20 is electrically connected to the isolated area 12a of the lower ITO transparent electrode film 12. Both end portions of the substrate 10 are provided with clip electrodes 24, 26 for drawing electrodes. The clip electrode 24 is electrically connected to the lower ITO transparent electrode film 12 and the clip electrode 26 is electrically connected to the upper ITO transparent electrode film 20. A transparent sealing resin 28 is applied on the upper ITO transparent electrode film 12 and a transparent glass plate is adhered thereon as a transparent sealing member 30. Thus the laminated structure is sealed. According to the above construction, when voltage is applied to the clip electrode 24 as a positive polarity and to the clip electrode 26 as a negative polarity, both of the oxidation coloring layer 14 and the reduction coloring layer 18 are colored, and when the reverse voltage is applied (or short-circuited), both coloring layers 14 and 18 are bleached.
In a conventional EC device, the colors during the coloring mode for the mixture film 14 of iridium oxide and tin oxide are all blue and the color of the entire device is also blue. For this reason, the conventional EC device could not be provided in use when the color is important (that is, when it is not desired that variation in color is made in an image obtained through the EC device). For example, the digital camera now in use has a ND (Neutral Density) filter built-in and is constructed to dim the light by moving the ND filter to a front surface of an image pickup device such as a CCD (Charge Coupled Device) by means of a motor when the amount of incident light is great. Since a motor is not required in the case of dimming light by replacing the ND filter with the EC device, it is possible to reduce the size and lower the power consumption of the digital camera. However, since in the conventional EC device, the color during the coloring mode is blue so that the color of the picked-up image exhibits blue-based colors and it is difficult to balance the white color, the EC device can not be used in place of the ND filter.